Yea I know what you mean about that glob Doug, but you were pumping it at 1600 ISO, gee mate I don't go much past 400, but that is just me, I think your skies might be a bit darker than mine.
I know INCN is a bugger at times and doubles your time but it is really worth the effort, have you tried it over two nights and then combine both nights.
IMHO, maybe the background is smoother because there is less light to pick up, less than the actual object, can't really help much with that one, I'm not that experienced
Leon